Okay, so... I got a DeWitt Clinton engine from eBay a few days ago (single boxed engine and tender) and it ran when I got it... but due to it's age, was a bit loud. So I bought some oil for it... "Liberty Oil" that, according to the sales page, was specially formulated for "Bachmann engines", plastic safe... all of that. I put a drop on each axle gear (on the tender, that's where the motor is) and then attempted to run it. Now, all it does is short out the track.

Any ideas here? This is my second DeWitt Clinton with issues now (the first one, one of the drive wheels likes to fly off on the track, and if you put it back on too tight, it shorts everything out) so if it's something I can fix at home, I'd prefer it.